40 Ar/ 39 Ar geochronology of copper mineralization and regional alteration, Mount Isa, Australia

Part II. Evaluation of 40Ar–39Ar quartz ages: Implications for fluid inclusion retentivity and determination of initial 40Ar/36Ar values in Proterozoic samples

“…7. The apparent age and estimated mica closure temperature plot close to the interpreted regional cooling trajectory and are compatible with an interpretation whereby sample AW02-002 formed during regional fluid flow and mineralization at Mt Isa ($1523 Ma; Perkins et al, 1999) and cooled through the effective closure temperature of variably sized accidentally trapped mica at $1030 Ma. The intra-sample remobilization of 40 Ar in the different samples is summarized graphically in Fig.…”

“…The above apparent ages are 100's of Ma younger than the preferred $1523 Ma age of Cu-mineralization at the nearby Mt Isa mine, that has been constrained by textural relationships, Ar-Ar biotite ages and Pb-isotope data (Swager, 1985;Perkins et al, 1999;Carr et al, 2004). It is possible that the Railway Fault is unrelated to mineralization at Mt Isa, and that the $1030 Ma age represents the time of movement on this fault.…”

Geology and Mineralogy of Uranium Deposits from Mount Isa, Australia: Implications for Albitite Uranium Deposit Models

“…The latter structures cut and displace uranium deposits and are implicated in sediment-hosted copper formation at Mount Isa [14]. Regional hydrothermal alteration within rocks of the ECV in the vicinity of Mount Isa has been extensively documented, mostly in the context of tracing flow paths for oxidised brines that formed the Mount Isa copper deposits [5][6][7]12,[15][16][17]. Of most relevance to this study are albite (± tremolite), carbonate-iron oxide and tourmaline types.…”

“…Additionally, enrichment in Na, Ca, P, Sr and F with depletion in K, Ba and Si has been noted at Valhalla [3]. Ar-Ar and U-Pb isotopic dates have been obtained from three of the deposits [3,7,8] and stable isotope data obtained from Valhalla [3]. Many of the deposits listed in Table 1, however, have not been previously described.…”

Part I. Decrepitation and degassing behaviour of quartz up to 1560°C: Analysis of noble gases and halogens in complex fluid inclusion assemblages

“…The sense of movement, strike direction and relative age of the Railway Fault together with the high Cu-content of fluid inclusions in this sample have previously been used to suggest a link with Cu mineralization ($1523 Ma; Perkins et al, 1999) at the Mt Isa mine (A. Wilde, Pers. Comm.…”